Don't log the diff renderer probe in the command log (#6112)

If a diff renderer is configured, its command shows up in the command
log once after startup, although the user didn't do anything. This is
the probe that asks the renderer whether it emits OSC 1717 metadata. It
changes nothing, so like other read-only commands it shouldn't be
logged.

pkg/commands/git_commands/diff.go

@@ -124,7 +124,7 @@ func (self *DiffCommands) probeFiles() (string, string, func(), bool) {
 }
 
 func (self *DiffCommands) probeEmitsMetadata(cmdObj *oscommands.CmdObj) bool {
-	cmdObj.AddEnvVars("OSC1717=V1")
+	cmdObj.AddEnvVars("OSC1717=V1").DontLog()
 	// A renderer may well object to being handed nothing to render. We want to know
 	// whatever it said before objecting, and that is captured either way.
 	output, _ := cmdObj.RunWithOutput()